[Scintigraphic studies of gonadal burden in radiosynoviortheses of the knee joint with yttrium 90].

Yttrium-90 radiosynoviorthesis of the knee joint in rheumatic inflammatory diseases shows favourable results. Because of the supposed exposure of the patients gonads, Yttrium synoviorthesis has rarely been performed in patients below the age of 40. Scintigraphic studies in 20 patients with rheumatoid arthritis showed no significant leakage of the radionuclide from the knee joint. Gamma camera measurements both phantom and in vivo in the regions of ovary and testes revealed a local dose of 1.05 microGy/MBq (3.9 mrd/mCi) or 1.1 microGy/MBq (4.1 mrd/mCi) of the injected radioactivity. Calculation of the maximum possible load of the gonads, supposing even total leakage of the injected 90-Yttrium from the knee joint, yielded a maximum possible dose of 6 mGy (600 mrd). We conclude from these studies and calculations that Yttrium-90 synoviorthesis of the knee joint can safely be carried out in patients below the age of 40.